System of helicopter screws



May 15, 1923.

1,454,944- vR. P. PESCARA S-YSTEM 0F HEIICOP'IER SCREWS Filed July l5 1920 Jn verl for:

'Patented' May 15,- 19223.

UNITED STATES l nAUnrATERAs rEscARA, or BARCELONA, SPAIN.

SYSTEM F HELICOPTER SGREWS.

Application mea ,my 15, 1920.I se'ial No. 396,597.

@To all whom it may concern:

Be it known that RAUL PATnRAs ESCARA," Acitizen"oi the Argentine Republic', and residing at Barcelona, Calle de la Buena Suerte 20, Spain, has invented new and useful Improvement in Systems of Helicopter' Screws (for which I have filed an application in Spain under date of July 3, 1919), of which the following vis/a specification. 10. This inventionA relates to a helicopter. l In matters dealing with helicopteration I designate by the word screw every organ adapted to give a pressurev or drivekby means ofthe rotation on an axis of surfaces constructed with or without.helicoidaltorsion The most'simple solution of the general type, maybe considered as by means of the u`se o f a s stem of-two screws turning vin inverse directions,` which may be inclined from the vert1cal in any dlrection.

The problem having 'thus been stated theoretically it is not, however, an easy mat- 25 ter to give it a practical solution in consequence of all the complications which the realization of the inclining of the apparatus -entails andwhich have to be overcome. On the other hand, when it is considered,

that in case of 'the accidental stoppingbf one or more motors of the helicopter, the descent, under the action of the machines own weight, would become accelerated in a manner to prove very dangerous, which would result in finding oneself in' the presence of serious diiiculties not of the .nature to encourage the studying and investigation of apparatus of this type. f

As a matter of fact the use of two-pro- 40 pellers turning inversely has for its object to counteract or oppose the pivoting movement' of the machine, such as the same wouldotherwise take up under the re-active influence of1-one-single propeller.

It is therefore apparent that such an arrangement-would not suiiice in itself to assure the stability of the orientation ofposition. It is evident, also, that two propellers cannotbe constructed with a rigorously exact perfection and that consequently some slight differences in theirangles of attack might exist in same. These discrepancies between the two propellers revolyingin inverse' directions would necessarily entail a more or less rapid pivoting df thel entire machine itself.

On the other steering, `the apparatus must change its orientation or position and it will benecessary to overcome this pivoting movement by means-of a special controlling or steering gear.

The system between the screws of Sustentation, propulsion, stabilization, parachuting and differential warping. in connection with flying machines' of the helicoptipal type as regards direction, propulsion and stability by inclining which is the objective of the present descriptive account, Ais destined to give a practical solution, by its sole action, of the problem of Direction; Propulsion; and' f Stability; p L

Easy descent without dependence on m0- tive power; i

Braking the descent when landing;

Stability of position (orientation) by the use, for obtaining these respective ef-.

fects, of

Periodical dilerential warping. Periodical and variable differential incidence. l Simultaneous' diminution and increase of the angle of attack of ,the propeller blades.

Differential warping between the propellers 'of the system.

Inv a general way, 1t is to be understood that, by the warping of the propeller blades, is meant a mechanical action which consists of causing a varying inthe angle of 'attack of the surfaces formed by the4 -said blades, in such manner that this variation only affects one partmore or less ex.- tended-of the total surface of the blades.

v The warping will be termed differential if,

hand in order to eil'ect the to an increase of incidence in one blade, there corresponds, at the same moment, a co-relative' diminution in the opposite blade. In short, I will designate it as periodical differential when the diii'erential variation of the angle of attack is reproduced periodically at each revolution of the blade.

The same definitions should be understood of theperiodical, variable differential va-l following manners that the variations of the angle of attack (as mentioned in the foregoing) affect the total of the surfaces which constitute vthe blades.

I term simultaneous decrease or increase of incidence in propellers, those screws constructed in such manner, that it is possible, during fiight, to diminish or increase the incidence of their blades; the diminution brought about at any given moment being equal as regards all the blades of the propeller under consideration.

In fact, the warping, which we have already dened above, will be designated differential as between the screws of the system, if, at the same time that the angles of attack in all the blades of one propeller are increased (that is -to say` partially) by means of the action of warping, a dimlnu-l tion is made in the same manner of these same corresponding angles on the other propeller of the system.

At the outset I will demonstrate the analogy which exists between the variable periodicwarping, and the variable periodical variation of incidence.

From these definitions it isievident that the warping, which affects a portion (generally a small part only) of the surfaces which form the blades, allows of efforts much more graduated in intensity being obtained than with the variation of differential incidence. 4

I therefore consider it. as .an improvement of the variable incidence, and to summarize it, I will consider anddeal with the possibility of using them 1n one of the three i (1). Variable incidence alone;

(2). Warping alone; (3). Warping and variable differential incidence, in combination.l

But, inasmuch as the reasoning which canbe applied to the aboveis the same both for the' warping and the variation of inci# dence, I will only speak of the warpingV with a View to simplifying matters. It will be understood, therefore, that in the following remarks all 1that I state as regards the one applies equally to the other.

It is known that the periodical differential warping allows ofthe centering of the drive or push given by. the propellers and conse# quently to bring into ,effect a couple of forces capable of inclining'the apparatus. The result of this inclining'isthe formation of s( horizontal component of the drive which" brings about a translation in a determined sense. The problem therefore, as regards propulsion and direction, is solved in this way.

The stability problem cannot be solved otherwise than by an intervention of an antagonistic couple lof forces which jointly oppose' the perturburating couples due 'to atmospheric action of every kind. The pesuch propelling screws.`

be efficacious itis necessary that it should be in accordance with a systematized rule corresponding to the angle of attack in which the relation between the resistance and the f push shall be atits minimum (or iu the proximity of minimum) as near as it is possible to beobtained with the profile of the blades adopted, and in order that this condition can be established, the normal rotating speed of the blades must be maintained, however. diminishing instantaneously their angle of attack before the velocity of the fall becomes too greatly accelerated. i

This diminution of incidence in all the blades corresponds to the -definition I have given, i. e.. simultaneous diminution of incidenee. This therefore allows of accomplishing the direct rotating volplane A sharp increase inverselyrwill permit of lin'aking the descending movement at the momentof landing. In fact, from the general definition of differential warping between the two screws, it is easily deducted that. if a difference exists between the angles of attack of4 the said screws the same can be easily corrected -by increasing the incidence of the screw'that offers the least turning` resistance, and reducing it in the one that presents the great resistance.` In an analogous manner` it is evident that this same maneuver can give rise to an inequality which will allow of altering the orientation and direction of the courses steered.

This beine' demonstrated, I shall now proceed to indi ate the practical realization of The drawing attached hereto, represents a comprehensive vertical section of the central portion of the screws. ,y lIn the drawingz' The central tube, serves as an axis in common for the two screws 2 and 3 and the bosses or hubs 4 and 5 of which are connected up by means of ball bearings6.7, Sand 9." The central tube is constructed of two pieces joined together by the intermediate section 10 which serves at the same time as a support for the conical pinib'ns 11. These pinions reverse the move.

l the two screws.

Periodic differential warpz'ng.- The rod '14 is mounted for universal movement as at at 16 and 17 `two-socket joints are fixed and carry the arms 18 and 19 which traverse the centr-al tube crossing the grooved soci-:ets and 'which are fixed into the ball bearings at 20 and 21.

The outside ring of these bearings carries.

facing each blade, small connection rods 22 and 23 which are articulated therein. -.At its other vend this rod is joined by anotherv articulation to vspindles or guide rods 24 and 25 which are'slidable in the inside of the tubular longitudinalfame bearers 26 and 27. Cables 28 and 29 whichoperate the warping appliances are -attached Vto these guide rods. It might be well to here recall that by warping appliance is meant any apparatus which. by its direct action on the air, tends to increase or reduce theangrle ofattack, or the push or drive of the blade in the region equipped with such an arrangement.

This warping or winding; appliance may be constructed in several equivalent ways: for instance, by a special construction ofthe blade which allows the variation of its curved surface in a certain region, or else by a wing'. that is capable of being trimmed while also being movable around a hori zontal axis. will assume that this'second type has been adopted-and this appliance is. operated by the intermediary of an endless screw which transforms the'tensionyor-rei the left laxation of the cable in rotating movements of the sailor wing. Y It is .to be noted that .these endless screws must have contrary inclinations in respect to the serews2 and 3-so that yby atension applied to the cable 28 or a 'relaxation ofcable 29 an identical movement is' applied tol the respective wings or sails of the two screws.I l 1 l It is easy to understand that, if the pilot inclines e rod 1 4 the' angles of attack :of

mif the blades .will be diminishedv The s Ill connecting spindles 22 vand 23 have their articulation in the ball-bearings 20 whichl allows' of the eceentrical action of the bearing 20 without interfering with the rotating movements of the screw propellers.

The lever @tangier the mnual control of `arms traversing 'the central tube 1.

vthe pilot, operates through the medium of,

a crank 31, several guides such as 32, 33and 34 linked up to' each other by spindles 35 i and 36; under the impulse exerted of the lever. 30, the entire system of guides and spindles can be made to rise or to descend by the sliding displacement in the inside of the tube 1. The guides 33 and34`serve to' support 'the' interior ring of theball bearings 37 and 38 by thev intermediate use of To the outer ring ofV these bearings are attached, facing each blade, the small conn ccting links 39 and 40 of which the other, ends are attached to the parts 41 and 42 whichl constitute' screws, the threads of which are verylong. l The sleeves 41 and/42 are provided on theoutside with rectilinear grooves 43' and 44 which adjust themselves.

in' corresponding groovesjprovided by supportingarms 45-and46.`-

In the interior of the screws the frame supports 26 and 27', these being tapped to the samescrew thread.- v

lt is thereforel obvious, that if the pilot .operates the lever 30- inV such manner, for example, as to cause-the guides a'nd 34 to ascend, and with them the ball bearings 37 and 38,v then Athe small spindles 39 and 40 will force the threaded sleeves 41'and .42to` approach to or recede: 'from the axis of the apparatus.

Inasmuch as these sleeves cannot turn on themselves on account of the grooves 43 and 44 it is the threads of these which forms a solid part of the franiefbearers 26 and 27, which 41 and 42 are con necting i' aoA turn on themselves, by communicating their movement toftheblade in its entirety thus bringingr about a. diminution or increase of incidence throughout every part of the. screw or propeller-.a

Differential 1art1-ping v bleib/veentw screws.

-I have already inditedhow' the controlling opera-tion of the periodic warpin is'efl'ected by-means of the rod 14. 4S'At 4 is a wheel which4 allows the rod 14 to be turned on itself.- This movement :of the before mentioned rod is transformed, by means of the screw`48, into one of ascent or descent of the same in its entirety. The,

socket joints 16 and 17 are then obliged to follow up .in this movement simultaneously with the ball ybearings 20 and 21. The small spindles 22 and 23 convertthis vertical movement into a horizontal displacement of the guide rods 24 and 25. If, for instance, the rod 14 has ascended those at 24 and 25 willfc'ome-nea-rer the axis of the apblades; and in the Screw 3 ,to a diminution 130 ing, on said spindle and connected with the of such incidence.A `In this way the differ- While, in t e foregoing, I have described 4 the specific embodimentA of the invention,

as shown-in theaccompan ing drawing, it.

is nevertheless to be un erstood that `in,

carrying the invention into practice I may` resort to any and all modifications;` falling withinjthe scope of the appended claims'.

1. In a helicopter, a pair of oppositely rotating propellers each having movable blade portions, a rcentral hollow spindle mounting said propellers for frotation thereon, and mechanism including elements within said spindle,y for Aadjusting the blades and movable portions thereofl independently; 2. In a helicopter, a pair of propellers ,having blades, a central spindle mountingA said propellers for rotation thereon in opposite directions, said blades having movable portions, ringmembers floating on vsaid spindle and connected with the movable portions of sa-idblades, and a control .rod passing throu h said ring'members and fulcruined t erebetween 'whereby movement of said rod displaces the ring members to actuate the movable blade portions.

3. In a helicopter, a pair of propellers having movable" blades, -a central lspindle mounting said propellers for rotation thereon in opposite direction, said blades having movable portions, ring members iloatangular rod passing through said ring members and fulcnuned therebetween whereby angular movement of said rod' displaces the ring.

memlbers to actuate the movable blade portions, and means for actuating the movable blades. v

4. In a helicopter, a pair of propeller having movable blades, a central" spindle mounting said `propellers forrotation thereon in opposite directions, said blades having movable portions, ring members floating on said spindle and connected with they `ing movable portions, ring members floating on said spindle and connected with the movable portions of,said blades, acontrol rod passing through said ring members and fulcrumed therebetween whereby angularA movement of said Yerod'displaces the' ring members to actuate the 'movable blade portions, means or actuating the. movable blades,v and means for moving the control rod along its axis.

In testimony whereof I, RAUL PATERAS PESCARA, have signed my name to this s ecifiycation in4 the presence of two subscri ing witnesses.

RAUL .PATERAS PESCARA.

`movable portions ofsaid blades, a. control 

